Nope, there is no reason that I can think of why Orchard would prevent that from working the exact same way as on static html. You'll probably need to do an in-depth comparison of the html and css in both cases to spot the difference.

Does anyone see a huge difference ?.. both codes work fine in Firefox and Chrome. The Top one works in IE 9 on a static page, but the bottom one for Orchard just won't make round corners in IE 9... what am i missing here ?

I know, that this isn't a webcoder forum, i just want to make sure, that it's not Orchard causing it...

if i implement it in Orchard, every browser i tested, ( chrome, ff, opera ) shows that circle EXCEPT IE 9.

I'm running out of options where that error may be in my files, and i start thinking that for some reason Orchard and IE 9 don't get along that well.

Does anyone have a working example of an Orchard generated page, on IE 9 with a round corner, created solely by css and not by graphics, htc files or anything else ?

EDIT: On a side note, one of my css menus stopped working in Orchard+IE9 aswell, didn't work anymore in Orchard+IE8 either.

However on a static page it also worked with IE8+9. Is there really nothing in Orchards interpretation that could cause those errors with IE ? Both things ( curves, menu ) are linked with <div></div>s so maybe that might be a point...

Cool, that's right for HTML5. There should also be a X-UA-Compatible meta tag in the head with IE=edge somewhere in the value to try to force IE into the most advanced rendering but it sounds like that's missing or something is overriding that (the
meta tag).

Is it a live/public site or something that IE might think is an intranet site?

If you hit F12 in IE9 to get the developer tools what does the "Document Mode" say?

that worked. With EmulateIE9 it also does the round corner, but some wierd font resizing aswell. But since i replaced the round corner with graphics now, so that they also appear in IE7+8, that's fine with EmulateIE8. Also solves the :focus problem.